#include<stdio.h>
int main()
{
	int i = 0;
	double sum = 0;
	int flg = 0;
	for(i = 1;i<=100;i++)
	{
		sum = sum +1.0/i*flg;
		flg= -flg;	
	}
	
	printf("%lf",sum);
	
	
	
	
	
	
	return 0;
 } 
